1. Department of Medicine, Imperial College London, Exhibition Road, London SW7 2AZ, UK
2. Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
3. Department of Medicine, University of Cambridge, Cambridge CB2 0QQ, UK
4. Royal Brompton Hospital and National Heart and Lung Institute, Imperial College London, Sydney Street, London SW3 6NP, UK
5. Division of Surgery and Cancer, Imperial College London, Praed Street, London W2 1NY, UK
6. Imperial Weight Centre, Imperial College Healthcare NHS trust, Praed Street, London W2 1NY, UK